Plasmon mass scale and quantum fluctuations of classical fields on a real time lattice

Aleksi Kurkela,Jarkko Peuron,Tuomas Lappi,M Della Morte,C Pena Ruano,E Gámiz Sánchez,P Fritzsch

doi:10.1051/epjconf/201817511001

Abstract

Classical real-time lattice simulations play an important role in understanding non-equilibrium phenomena in gauge theories and are used in particular to model the prethermal evolution of heavy-ion collisions. Above the Debye scale the classical Yang-Mills (CYM) theory can be matched smoothly to kinetic theory. First we study the limits of the quasiparticle picture of the CYM fields by determining the plasmon mass of the system using 3 different methods. Then we argue that one needs a numerical calculation of a system of classical gauge fields and small linearized fluctuations, which correspond to quantum fluctuations, in a way that keeps the separation between the two manifest. We demonstrate and test an implementation of an algorithm with the linearized fluctuation showing that the linearization indeed works and that the Gauss’s law is conserved.

Highlights

The Color Glass Condensate (CGC) [1] is an effective theory of QCD in the high energy limit
We argue that one needs a numerical calculation of a system of classical gauge fields and small linearized fluctuations, which correspond to quantum fluctuations, in a way that keeps the separation between the two manifest
We have studied the plasmon mass in pure glue QCD using three different methods: the effective dispersion relation, the uniform electric field method and perturbative formula relating the quasiparticle spectrum to the plasmon mass

Summary

Introduction

The Color Glass Condensate (CGC) [1] is an effective theory of QCD in the high energy (weak coupling) limit. In particular CGC predicts that gluon states of nonperturbatively high occupation numbers (> 1/g2) are created in the initial stages of ultrarelativistic heavy ion collisions [2,3,4]. Due to the expansion of the system, the typical occupation numbers of the gluon states decrease over time. When they become perturbative, the system admits a kinetic theory [5] description. After subsequent hydrodynamical evolution the system expands and cools down, and freezes out

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Conclusion